Cross-linked Polyethylene - Uses - Benefits and Drawbacks

Benefits and Drawbacks

Benefits of using PEX in plumbing include:

• Flexibility. PEX has become a contender for use in residential water plumbing because of its flexibility. It can bend into a wide-radius turn if space permits, or accommodate turns by using elbow joints. In addition, it can handle short-radius turns, sometimes supported with a metal brace; in contrast, PVC, CPVC and copper all require elbow joints. A single length of PEX pipe cannot handle a sharp 90-degree turn, however, so in those situations, it is necessary to connect two PEX pipes with a 90-degree PEX elbow joint.

• Direct routing of pipes. PEX can run straight from a distribution point to an outlet fixture without cutting or splicing the pipe. This reduces the need for potentially weak and costly joints and reduces the drop in pressure due to turbulence induced at transitions. Since PEX is flexible, it is often possible to install a supply line directly from the water source to an appliance using just one connection at each end.

• Greater water pressure at fixtures. Since PEX pipes typically have fewer sharp turns, there is greater water pressure at the sinks and showers and toilets where it is needed.

• Less materials cost. Cost of materials is approximately 25% of alternatives. One account suggested that the price of copper had quadrupled from 2002 to 2006.

• Easier installation. Installing PEX is much less labor intensive than copper pipes, since there is no need to use torches to solder pipes together, or to use glue to attach pipes to fittings. One home inspector wrote that "Once you've worked with PEX, you'll never go back to that other stinky glue stuff." Builders putting in radiant heating systems found that PEX pipes "made installation easy and operation problem-free." PEX connections can be made by pushing together two matching parts using a compression fitting, or by using an adjustable wrench or a special crimping tool. Generally, fewer connections and fittings are needed in a PEX installation.

• Reliable. It neither corrodes nor develops so-called "pinhole" leaks.

• No fire risk during installation. Copper piping required soldering using torches, and there was a risk of flame and heat causing a fire; but with PEX there is virtually no danger from fire. However, there was an unfortunate counter-incident in 2011 in which authorities suspect that six firefighters were injured when a fire melted the plastic PEX pipes, causing water to soak into ceiling insulation, adding greater weight which caused the ceiling to collapse; but the PEX tubing was not blamed as the cause of the fire. Overall PEX piping is much safer to install; according to the U.S. National Fire Prevention Agency, torches used for soldering metallic plumbing ranked as one of the "top-ten leading causes of house fires each year."

• Acceptance by plumbers. There are routinely advertisements for plumbers specifically seeking ones with PEX experience.

• Ability to merge new PEX with existing copper and PVC systems. Manufacturers make fittings allowing installers to join a copper pipe on one end with a PEX line at the other, as well as have options to reduce or expand the diameter of the pipes.

• Longevity. The advantageous properties of PEX also make it a candidate for progressive replacement of metal and thermoplastic pipes, especially in long-life applications, because the expected lifetime of PEX pipes reaches 50 years. However, the longest warranty offered by any PEX producer is 25 years.

• Suitable for hot and cold pipes. A convenient arrangement is to use color coding to lessen the possibility of confusion. Typically, red PEX tubing is used for hot water while blue PEX tubing is used for cold water.

• Less likely to burst from freezing. The general position is that PEX plastic materials are slower to burst than copper or PVC pipes, but that they will burst eventually since freezing causes water to expand. One account suggested that PEX water-filled pipes, frozen over time, will swell and tear; in contrast, copper pipe "rips" and PVC "shatters". Home expert Steve Maxwell suggested in 2007 that PEX water-filled pipes could endure "five or six freeze-thaw cycles without splitting" while copper would split apart promptly on the first freeze. In new unheated seasonal homes, it is still recommended to drain pipes during an unheated cold season or take other measures to prevent pipes from bursting because of the cold. In new constructions, it is recommended that all water pipes be sloped slightly to permit drainage, if necessary.

• No corrosion. Copper and iron pipes can experience corrosion leaks but PEX does not have these problems.

• Environmental benefits. One account suggested that PEX used in radiant heating was better for the environment than a copper choice, although it noted that the pipes were based on petroleum products.

• Pipe insulation possible. Conventional foam wrap insulation materials can be added to PEX piping to keep hot water hot, and cold water cold, and prevent freezing, if necessary.

Drawbacks of PEX piping include:

• Degradation from sunlight. PEX tubing cannot be used in applications exposed to sunlight, as it degrades fairly rapidly. Prior to installation it must be stored away from sunlight, and needs to be shielded from daylight after installation. Leaving it exposed to direct sunlight for as little as 30 days may result in premature failure of the tubing due to embrittlement.

• Problems with yellow brass fittings. There have been some claimed PEX systems failures in the U.S., Canada and Europe resulting in several pending class action lawsuits. The failures are claimed to be a result of the brass fittings used in the PEX system. Generally builders and manufacturers have learned from these experiences and have found the best materials for use in fittings used to connect pipe with connectors, valves and other fittings. But there were problems reported with a specific type of brass fitting used in connection with installations in Nevada which caused a negative interaction between its mineral-rich hard water and so-called "yellow brass" fittings. Zinc in the fittings leached into the pipe material in a chemical reaction known as dezincification, causing some leaks or blockages. A solution was to replace the yellow brass fittings which had 30% zinc with red brass fittings which had 5% to 10% zinc. It led California building authorities to insist on fittings made from "red brass" which typically has a lower zinc content, and is unlikely to cause problems in the future since problems with these specific fittings have become known.

• Initial adjustment to a new plumbing system. There were a few reported problems in the early stages as plumbers and homeowners learned to adjust to the new fittings, and when connections were poorly or improperly made, but home inspectors have generally not noticed any problems with PEX since 2000.

• Can't use adhesives for pipe insulation. One source suggested that pipe insulation, applied to PEX using certain adhesives, could have a detrimental effect causing the pipe to age prematurely; however, other insulating materials can be used such as conventional foam wrap insulation without negative effects.

• Fittings somewhat more expensive. Generally PEX fittings, particularly the do-it-yourself compression ones, are more expensive than copper ones, although there is no soldering required. Due the flexibility of PEX, it generally requires fewer fittings, which tends to offset the higher cost per fitting.

• Potential problems for PEX radiant heating with iron-based components. If PEX tubing is used in a radiant heating system which has ferrous radiators or other parts, meaning they are made out of iron or its alloys, then there is the possibility of rust developing over time; if this is the case, then one solution is to have an "oxygen barrier" in these systems to prevent rust from developing. However, in new installations PEX pipes and iron-based components are not intermixed.

• Possible health effects. There was controversy in California during the 2000s about health concerns. Several groups blocked adoption of PEX for concerns about chemicals getting into the water, either from chemicals outside the pipes, or from chemicals inside the pipes such as methyl tertiary butyl ether and tertiary butyl alcohol. These concerns delayed statewide adoption of PEX for almost a decade. After substantial "back-and-forth legal wrangling" which was described as a "judicial rollercoaster", the disputing groups came to a consensus, and California permitted use of PEX in all occupancies. An environmental impact report and subsequent studies determined there were no causes for concerns about public health from use of PEX piping.